2-Dimethylamino-l,3,4-oxadiazole

Reaction of a hydrazide (128) with phosgeneiminium chloride (115) led to the 2-dimethylamino-l,3,4-oxadiazole (129) in 90% yield (75AG(E)806). The 1,3,4-thiadiazole system was also obtained in an analogous reaction in which the dithioimidate (130) underwent reaction with the thiohydrazide (131). Depending on the nature of X in (131), the 2-substituent in the resultant 1,3,4-thiadiazole (132) may be varied (80ZC413). Although (130)... 

Reaction of a hydrazide with dichloromethylene-dimethyliminium chloride (also known as phosgeneimonium chloride) 597 led to the 2-dimethylamino-l,3,4-oxadiazole 598 (Scheme 268) <1973AGE806>. The 1,3,4-thiadiazole 601 was made by an analogous reaction from 599 and 600 (Scheme 269). 

The internal rotation barriers of the dimethylamino groups in substituted azoles including 5-nitro-2-dimethylamino-l,3,4-oxadiazole (AG =9 kcal/mol, 133°C) were also defined by NMR spectroscopy [523],... 

As a rule, oxadiazoles and thiadiazoles are not nitrated. Reports on the production of 2-nitro-5-amino-l,3,4-thiadiazole during the nitration of 2-amino-l,3,4-thiadiaz-ole [274] proved erroneous [275], The compound obtained in this case was 2-nit-ramino-l,3,4-thiadiazole [275], There is only a single paper on the nitration of derivatives of 1,3,4-oxa- and 1,3,4-thiadiazoles [276], 2-Dimethylamino-l,3,4-oxa-and 2-dimethylamino-l,3,4-thiadiazoles react with the nitrating mixture with the formation of 2-dimethylamino-5-nitro derivatives. Aryl-substituted oxadiazoles and thiadiazoles are nitrated in the phenyl ring [277, 278],... 

Dimethisterone (see also Progestins Sequential oral eontraeeptives) Dimethoxane 3,3 -Dimethoxy benzidine 3,3 -Dimethoxybenzidine-4,4 -diisocyanate para-Dimethylaminoazobenzene / ara-Dimethylaminoazobenzenediazo sodium sulfonate tra 5-2-[(Dimethylamino)methylimino]-5-[2-(5-nitro-2-furyl)-vinyl]-l,3,4-oxadiazole... 

Thus, 2-imino-3-methyl-5-phenyl-l,3,4-oxadiazoline is obtained from the methylation of 2-amino-5-phenyl-l,3,4-oxadiazole with methyl iodide.61,63 Only in a sealed tube with an excess of methyl iodide is 2-methylimino-3-methyl-5-phenyl-1,3,4-oxadiazoline formed.63 The structure of the alkylated product was confirmed by its nonidentity with 2-methylamino-5-phenyl-l,3,4-oxadiazole or 2-dimethylamino-5-phenyl-l,3,4-oxadiazole which were synthesized by an independent route. 

Few pK values of 1,3,4-oxadiazoles have been measured, partly because of the poor water solubility of aromatic substituted oxadia-zoles. A pKb value of 11.63 (in water) is given for 2-amino-5-methyl-1,3,4-oxadiazole.156 2-Amino-5-phenyl-l,3,4-oxadiazole and its mono-and dimethylamino derivatives have approximate pKa values between 2.3 and 2.7 (in 50% alcohol).63 On the other hand, the pKa values of... 

Poly(9,9 -dihexylfluorene-2,7-divinylene-m-phenylene vinylene-stat-p-phenyl-ene vinylene), 30, 31, 51 Poly(2,5-dimethoxy-l,4-phenylene vinylene), 95 Poly(2-(A, A -dimethylamino) phenylene vinylene), 100 Poly(2-dimethyloctylsilyl)-phenylene vinylene, 99 Poly(9,9-dioctylfluorene), 31, 110 Poly(9,9-dioctylfluorene-co-lluorenone), 30 Poly(4,4 -diphenyl ether-l,3,4-oxadiazole), 334 Poly(2,6-diphenyl-l,4-phenylene oxide), 152 Poly(2,6-diphenyl-l-4-phenylene oxide), 141 Poly(dithiathianthrene), 189 Poly(2-dodecyl-p-phenylene), 36 Poly(AT-epoxypropyl)carbazole, 13 Poly(ether ether ketone), 209 Poly(ether imide), 154, 214, 264, 376 Pol(yether ketone), 213 Poly(ether nitrile), 227 Poly(ethersulfone), 209, 264... 

Glyoxylsaure -(4-dimethylamino-phenylnitron)-nitril X/4, 399 Hydrazin 2-Cyan-l-(3-phenyl-propanoyl)-X/2, 130 Imidazolidin 2-[2-Oxo-2-(3-pyridyl)-ethyliden]- E15/2, 2003 [aus S-(2-Oxo-alkyl)-cycl.-isothioharnstoffj lH-Isoindol 3-(2,2-Dimethyl-hydrazono)-l -oxo-2,3-d ihydro-E16a. 790 (N,N-Aufbau) 1,2.4-Oxadiazol... 

Semenova, O. N., Galkina, O. S., Patsenker, L. D., Yermolenko, I. G., Fedyunyayeva, I. A. Experimental and theoretical investigation of the reaction of 2,5-diphenyl-1,3-oxazole and 2,5-diphenyl-1,3,4-oxadiazole dimethylamino derivatives with the Vilsmeier reagent. Functional Materials 200i, 11,67-75. 

The reaction of 5-[2-(iV,./V-dimethylamino)ethyl]-l,2,4-oxadiazole with methyl iodide forms the quaternary ammonium salt 170 (Scheme 22), which undergoes elimination in the presence of base (diisopropylethylamine (DIEA), TEA, l,8-diazabicyclo[4.3.0]undec-7-ene, etc.) to form an intermediate 5-vinyl-l,2,4-oxadiazole 171, which undergoes in situ Michael addition with nucleophiles to furnish the Michael adducts 172. As an example, also shown in Scheme 22, 3-hydroxy-pyrrolidine allows the synthesis of compound 172a in 97% yield. Mesylation followed by deprotonation of the 1,2,4-oxadiazole methylene at C-5 enables Sn2 displacement of the mesylate to give the 5-azabicycloheptyl derivative 173, which is a potent muscarinic agonist <1996JOC3228>. 

Nitrosation of methyl 2-acylamino-3-(dimethylamino)propenoates 494 obtained from the corresponding oxazolones 493 effects the conversion of A -acylglycines to 5-substituted-l,2,4-oxadiazole-3-carboxylates 496 as shown in Scheme 7.157. ... 

Amino-hydroximino-methyl)-pyridin liefert mit Dimethylamino-trichlor-methan beim Sie-den in Acetonitril 5-Dialkylamino-3-(2-pyridyl)-l,2,4-oxadiazol (29% Schmp. 82—85°)113 ... 

Dimethylamino-phenylimino)-oxido-methyl]-2-methyl-5-phenyl-l,2,4-oxadiazol-2-onium 28% Schmp. 162 164°... 

Ar-[(Ar,Ar-Dimethylamino)methylene]pyrido[2,3-c/]pyrimidin-4-amine 3-oxide (6) plays a central role as an educt for 3-(3-pyridyl)-l,2,4-oxadiazoles. Thus, it has been treated with carbon nucleophiles such as the anions of diethyl malonate, ethyl cyanoacetate, or pentanc-2,4-dione.417 After addition across the 2,3-bond, ring opening of the pyrimidine moiety with simultaneous 1,2,4-oxadiazole ring formation occurs. Evidently, the five-membered ring is formed easily through participation of the [(dimethylamino)methylene]amino and TV-oxide functions. 

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